X-ray tube



A. BOUWERS July 8, 1930.

X-RAY TUBE Filed Feb. 12 1926 I 2 Sheets-Sheet 1 A. BOUWERS July 8,1930.

X-RAY TUBE 2 Sheets-Shee1'. 2

Filed Feb. 12 1926 Patented July 8, 1930 UNITED STATES PATENT OFFICEALBERT ."BO'UWERS, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO N. V. PHILIPS'GLOEILAMPENFABRIEKEN, OF EINDHOVEN, NETHERLANDS X-RAY TUBE Applicationfiled February 12, 1926, Serial No.

said metal part, and has for its object to intercept within the tube therays which do not contribute to the cone of active X-rays, so as tosafeguard the operator of the tube.

According to the invention one or more screens are arranged within thetube whereby the X-rays are prevented from leaving the tube throughparts of the glass wall not designed for this purpose.

The metal wall of the tube may be electrically connected to theanticathode; preferably, however, the anticathode is insulated from themetal part of the outer wall in such a manner that the-insulation iscapable of resisting the operating voltage to be supplied between theearth and the anticathode. The

invention may be applied for example, to X- ray tubes as describedinapplication, Ser. No. 673,166, filed November 6, 1923 and patented asPatent 1,626,465, April 26, 1927 said tubes bein provided with anincandescent cathode whic is brought up to substantially the samepotential as that of the outer wall. The invention may also beadvantageously applied to X-ray tubes as described in my application,Ser. No. 5,108, filed January 27, 1925 in which tubes the cathode andthe anticathode are insulated from the metal part of the outer wall,said insulations together being capable of resisting the operatingvoltage occurring between the cathode and anticathode.

In an embodiment of the invention, a cathode is surrounded by a metalvessel which is insulated from the metal part of the wall of the tube,and which during the operation of the tube, is given the same potentialas or a slightly differing potential from that of the cathode, the metalscreen being secured in the said vessel behind the cathode. According tothe invention this metal screen may serve at the same time as a supportfor the cathode.

Moreover, if the presence --of a screen behind the cathode is not initself sufiicient to intercept all the rays that are not active, anannular metal screen may be secured to the outer wall of the vesselsurrounding the oath 'difiicult for these rays to penetrate.

87,795, and in the Netherlands April 6, 19'25.

ode. In this case the said annular screen has to be arranged in such amanner as to intercept the non-active X-rays emanating from theanticathode and penetrating through the free space between the vesselsurrounding the cathode and the metal part of the outer wall.

The metal screen serving to intercept X- rays, must consist of amaterial which it is Also, it is advisable to make the screen of ahighly refractory material seeing that by heat conduction or by heatradiation it is frequently heated to a high temperature. Very favourableresults are obtained with a screen consisting of tungsten.

The invention will be more clearly understood with reference to theaccompanying drawings in which: I

Figure 1 represents an X-ray tube comprising an incandescent cathodesupported by a screen for intercepting the undesired rays, said screenbeing in direct contact with the metal part of the wall of the tube.

Figure 2 represents an X-ray tube in which an incandescent cathode issurrounded by a metal vessel which is insulated. from the metal part ofthe outer wall and to which is secured a metal screen arranged behindthe incandescent cathode in addition to an annular'metal screen beingarranged around the said vessel.

Figure 3 represents an X-ray tube of a construction similar to thatshewn in Figure 2, differing, however, in that the annular metal screenaround the vessel surrounding the incandescent cathode is omitted, asthe construction of the tube makes such a screen superfluous.

.Figure 4 represents an embodiment of the invention in which only anannular metal screen is arranged around the vessel surrounding theincandescent cathode, the space within the vessel being left free forthe passage of the cone of active X-rays.

To a metal part 1 of the outer wall of the X-ray tube illustrated inFigure 1 is sealed a glass part 2 which carries an anticathode 3.-To'the metal part 1 is also sealed a second glass part 4, having sealedin it the leadingin wires for an incandescent cathode 5. The

metal part 1 of the wall may consist, for ex 100 ample, of chrome iron,or in general of a material which allows of being readily sealed toglass and which does not readily transmit X- rays. In the metal part ofthe wall is pro vided a window 6 for the passage of the active X- re s.

A s c reen 7 for intercepting X-rays emitted by the anticathode anddirected to the glass part 4 of the wall, is fixed, by welding or in anyother manner, to a receiving edge of the metal part, of the wall. Thisscreen may serve in addition as a support for the incandescent cathode,for which purpose the leading-in wires are insulatingly carried by thescreen.

Fi ure 2 represents a construction princ'ipal similar to the X-ray tubedescribed in specilihation No. 5,108 previously mentioned.

In this construction a metal part 11 of the' wall is sealed on one sideto a glass part 13 which carries an anticathode 14 and on the other sideto a glass part 15 carrying a vessel 16 in which is mounted anincandescent cathode 17, said metal part being provided with a window 12for the passage of the cone of active X-rays. In the constructionillustrated the incandescent cathode consists of a helix which on oneside is secured to a leading-in wire 18 and on the other side to a metalvessel 16 to which is connected at leading-in wire 19. The vessel 16therefore has the same potential as the incandescent cathode 17 so thatthe electrons emanating from this cathode, are drawn substantiallytowards the anode, which during the operation of the tube has a highpotential.

Inside the X-ray tube is arranged a metal screen 20, preferably, oftungsten, which rests on a collar of the vessel 16. This screen servesto intercept X-rays penetrating into the vessel 16. As the screen 20 isbrought up to the same potential as the vessel 16, it will also attractbut few electrons emanating from the cathode so that the electronsemitted are directed to the anticathode to a still larger extent. Thescreen 20 also serves to support the incandescent cathode, for whichpurpose the leading-in wire 18 is insulatingly carried by the screen 20.

A second screen 21, likewise of tungsten, is arranged around the vessel16 and intercepts the X-rays emanating from the anticathode andpenetrating through the space between the metal part 11 of the Wall andthe metal vessel 16. All the rays which might be dangerous to theoperator of the X-ray tube are lntercepted by the metal wall 11 and thetwo screens 20 and 21.

The X-ray tube illustrated in Figure 3, is substantially similar to theconstruction shewn in Figure 2. Similar members in this figure arereferred to by the same reference numerals. This tube is provided withan incandescent cathode 25 constituted by a straight filament, oneleading-in wire 18 of which is insulatingly carried by a metal screen20, another leading-in wire 26 being electrically connected to the saidscreen 20. In this construction the metal part 11 of the outer wall isconstructed in such a manner that the X-rays are prevented from leavingthe tube through the space between the vessel 16 and the wall 11. Inthis construction the annular screen 21 represented in Figure 2 istherefore superfluous.

Figure 4 represents an embodiment of the invention in which the openspace within the vessel surrounding the cathode serves for the emissionof the cone of active X-rays. In

this figure similar members are indicated by the same reference numeralsas in F igure 3. In this construction a glass part 27 sealed to a glasspart 15 of the wall serves as a Window. A cathode 25 carried by a metalvessel 16 is on one side electrically connected thereto whereas theother end of the cathode is secured to a leading-in wire 28 which iscarried by the metal vessel .16 from which it is insulated. A tungstenscreen 29 serving to intercept X-rays which would be dangerous to theoperator of the tube, and which might leave the tube through the spacebetween the vessel 16 and the part 11 of the wall, is arranged aroundthe vessel 16 and rests on a collar of the vessel 16.

What I claim is 1. An X-ray tube the wad of which consists partly ofmetal, in which the cathode and the anticathode are surrnanded for thegreater part by said metal part, a metal vessel surrounding the cathodand insulated from the metal part of the wall of the tube, a screenfixed in said vessel behind the cathode, said screen being diflicult forX-rays to penetrate, whereby the X-rays are prevented from leavin thetube through parts of the wall not designed for this purpose.

2. An X-ray tube the wall of which consists partly of metal, in whichthe cathode and the anticathode are surrounded for the greater part bysaid metal part, a metal vessel surrounding the cathode and insulatedfrom the metal part of the wall of the tube, a screen fixed in saidvessel behind the cathode, said screen supporting the cathode and beingdifficult for X-rays to penetrate, Whereby the X-rays are prevented fromleaving the tube through parts of the Wall not designed for thispurpose.

3. An X-ray tube the wall of which consists partly of metal, in whichthe cathode and the anticathode are surrounded for the greater part bysaid metal part, a metal vessel surrounding the cathode and insulatedfrom the metal part of the wall of the tube, an annular screen securedto the outer wall of said vessel, said screen being diificult for X-raysto penetrate, whereby X-rays are prevented from leaving the tube throughparts of the wall not designed for this purpose.

4. An X-ray tube the Wall of which consists partly of metal, in whichthe cathode and the anticathode are surrounded for the greater part bysaid metal part, a metal vessel surrounding the cathode and insulatedfrom the metal part of the wall of the tube, a screen fixed in saidvessel behind the cathode, and

